C. Hackman1, S.M. Byram1, V.J. Slabinski1, J.C. Tracey1

USNO Analysis Center Progress 2012-4
Naval Observatory, Washington DC;
Improvements in
Products = orbits, clocks, polar motion (PM)
Improvement = reduction in RMS wrt IGS Rapids
13-57% improvement in USNO ultra-rapids
6-25% improvement in USNO rapids
Causes:
• Improved tie to IGS reference frame
• Lengthened measurement window used for
ultra-rapid predictions to 40 h (was 27)
• Current precision: ~17mm/37 mm past/pred orbits;
~100 mas/300 mas past/pred polar motion
2012
2013
reduction in median, 2012 -> 2013:
rapids: 6%
ultra, past and pred: 23%
2014
120
49
48
AC HISTORY AND ACTIVITIES
44
40
37
100
80
30
mm
60
21
19
20
40
• AC since 1997
2010
17
15
2011
22
2012
2013
17
16
10
0
365
730
1095
days since 1 Jan 2010
1460
1825
0
ultra, pred
ultra, past
rapid
rapid
RMS, USNO GPS Clock Estimates wrt IGS Rapid Combined
Jan 2010 - May 2014
ultra, past
ultra, pred
reduction in median, 2012 -> 2013:
rapids: 6%
ultra pred: 35%
8000
2500
2930
2443
2296
1902
2000
2010
2010
2011
2012
2013
2014
• Ultra-rapids: post-processed &
predicted orbits, clocks, EOPS.
Every six hours; 3 hrs latent
2011
1500
2012
2013
1000
500
80
0
365
730
1095
days since 1 Jan 2010
1460
1825
124
145
155
146
0
ultra, pred
rapid
RMS, USNO GPS Polar Motion wrt IGS Rapid Combined
2013
micro
arc sec
2014
600
400
• Chair IGS Troposphere WG
277
200
300
235
0
2011
167
157
2013
116
130
79
100
-800
0
365
730
1095
days since 1 Jan 2010
dx, rapid
1460
1825
0
dy, rapid
dx, rapid
USNO Ultra-Rapid Polar Motion wrt IGS Rapid Combined
Jan 2010 - May 2014
2011
2012
2013
2014
1500
1000
micro arc sec
dx, ultra past dy, ultra past dx, ultra pred dy, ultra pred
• Produce UTGPS, a GPS-based
extrapolator of VLBI UT1-UTC
estimates, 5 times/day for IERS,
which uses it to improve UT1-UTC
predictions
Top row: weighted RMS of USNO GPS
orbit estimates with respect to IGS Rapid
Combination.“Ultra, past” refers to 24-hour
post-processed section of USNO ultrarapid orbits. “Ultra, pred” refers to first six
hours of ultra-rapid orbit prediction.
2000
2010
dy, rapid
500
0
Second row: RMS of USNO GPS rapid
clock estimates and ultra-rapid clock
predictions with respect to IGS Rapid
Combination
-500
-1000
-1500
-2000
0
365
730
1095
days since 1 Jan 2010
dx, pred
dy, pred
dx, past
1460
1825
r
Rows 3-4: USNO polar motion estimates
minus IGS Rapid Combination values.
dy, past
COMBINED GPS/GLONASS
Byram, S and C Hackman, High-Precision GNSS Orbit, Clock and EOP Estimation at the United
States Naval Observatory, Proc. 2012 IEEE/ION PLANS, 659-63, 2012.
• Have generated GPS+GLO ultras, rapids
since 2012
• Ultras under consideration for inclusion in
IGV combination
• In-house precision estimates:
• GLO orbits: 49 mm post-processed;
119 mm predict
• PM: ~100 mas
• More details: Byram & Hackman, “Multi-GNSS
Based Processing at the USNO,” PS11
Byram, S and C Hackman, IGS Final Troposphere Product Update, Poster Session PS05, 2014 IGS
Workshop, Pasadena, CA, 2014.
Byram, S and C Hackman, Multi-GNSS Based Processing at the USNO, Poster Session PS11, 2014
IGS Workshop, Pasadena, CA, 2014.
Dousa, J, S Byram, G Győri, O Bӧhm, F Zus and C Hackman, Development Towards Inter-Technique
Tropospheric Parameter Comparisons and Their Exploitation, Plenary Session PY09, 2014 IGS
Workshop, Pasadena, CA, 2014.
Hackman, C, GPS Code/Carrier-Phase Time/Frequency Transfer, IEEE International Frequency
Control Symposium Tutorials, 149 pp, 2012.
Hackman, C, Mitigating the Impact of Predicted Satellite Clock Errors on GNSS PPP Positioning, Proc.
ION 2014 International Technical Meeting, 743-50, 2014.
Hackman, C, Impact of Orbit, Clock and EOP Errors in GNSS Precise Point Positioning, 2012 AGU
Fall Meeting, oral presentation G13C-01, 2012.
Hackman, C, Accuracy/Precision of USNO Predicted Clock Estimates for GPS Satellites, Proc. 44th
Ann. PTTI Meeting, 43-52, 2012.
Hackman, C and S Byram, IGS Troposphere Working Group 2012, IGS Technical Report 2012, 195202, 2013.
Hackman, C and S Byram, IGS Troposphere Working Group 2013, IGS Technical Report 2013, in
press, 2014.
Hackman, C and D Matsakis, Precision and Accuracy of USNO GPS Carrier-Phase Time Transfer:
2012 Update, Proc. IEEE IFCS, 94-99, 2012.
USNO Test GPS+GLONASS Ultra-Rapid Polar Motion wrt IGU
24-h post-processed segments compared
25
500
400
20
300
200
cm
micro arc sec
15
10
100
0
-100
-300
RMS (x, y, micro arc sec): 115, 72
-400
median (cm): ultra, past: 4.9; ultra, pred: 11.6
0
-500
60
120
180
days since 1 Jul 2013
pred 6hr
past 24hr
240
300
360
0
60
120
180
days since 1 Jul 2013
dx, past
240
300
dy, past
Left: RMS of USNO ultra-rapid GLONASS orbit estimates wrt IGS Combined Ultra-rapid
GLONASS orbits. “Ultra, past” refers to 24-hr post-processed section of USNO ultra-rapid
orbits. “Ultra, pred” refers to first six hours of ultra-rapid prediction. Helmert transformations
computed using Bernese 5.0 Software. Right: Difference between 24-h post-processed polar
motion estimates in USNO test ultra-rapid GPS+GLONASS solution and IGS “IGU” GPS-only
ultra-rapid solution.
300
250
2011
mean: 322
2012
mean: 302
2014
mean: 328
2013
mean: 325
(+8% wrt 2012)
200
0
365
730
days since 1 Jan 2011
1095
1460
clickable station map, list
360
Web interface draft layout
graphs up to six
stations with multiple
technique
comparisons
user defined
comparison graph
AC GNSS Experiments
• Always testing new ideas in GNSS-based PNT
• E.g., recently tested GPS+GLO PPP
• Encountered pseudorange-based receiverdependent bias between GPS-, GLO-based
receiver-clock estimates
• Resolving…
GLO/GPS OFFSET EST'D FROM P-CODE
Experiment
• Obtained GPS+GLO
measurements from
seven receivers 10-21
Feb 2014
• Did PPP using GPS,
GPS+GLO and GLO
using EMR GLO/GPS
orbit products
• 24-hr batches; static
positioning
• Receiver-clock estimates
every 300 s
name
east
longitude,
deg
north
latitude,
deg
ellipsoidal
height, m
ALGO
-78
46
201
KARR
117
-21
109
MBAR
31
-1
1337
Hackman, C and J Tracey, Monitoring Signal Strength of China’s COMPASS/Beidou Satellite
Transmissions, Office of Naval Research Science and Technology Partnership Conference, Crystal
City, VA, 2012.
OHI2
-58
-63
32
STJO
-53
48
153
Hackman, C, S M Byram, V J Slabinski and J C Tracey, USNO GPS/GLONASS PNT Products:
Overview, and GPS+GLONASS vs GLONASS Only PPP Accuracy, Proc. 2014 IEEE/ION PLANS, in
press, 2014.
TRO1
19
70
138
WHIT
-135
61
1427
Hackman, C, S M Byram, V J Slabinski and J C Tracey, Near-Real-Time and Other High-Precision
GNSS-Based Orbit/Clock/Earth-Orientation/Troposphere Parameters Available from USNO, Proc.
2012 ION Joint Navigation Conference, 1274-88, 2012.
-200
5
• Total: 16 product sets per day; 98100% on-time rate
2012-4 Analysis Center Publications
RMS, 7-Par Helmert Transform btwn USNO, IGS Ultra-Rapid GLO Orbits
350
Number of stations for which IGS
Final Troposphere Estimates were
produced by USNO
• Above estimates generated using
Bernese GPS Software
99
-600
400
• Since 2012: produce test
GPS+GLONASS rapids, ultra-rapids
2010
2012
197
157
183
187
200
-400
160
132
-200
160
165
154
mirco arc sec
400
295
317
2012
336
2011
reduction in RMS, 2012 ->2013:
dx, rapid: 16%
dy, rapid: 25%
dx, ultra past: 57%
dy, ultra past: 51%
dx, ultra pred: 32%
dy, ultra pred: 13%
362
2010
491
500
800
314
USNO Rapid Polar Motion wrt IGS Rapid Combined
Jan 2010 - May 2014
• Produce IGS Final Troposphere
Estimates
ultra, pred
377
rapid
Number of Quality-Checked Troposphere Files Submitted to IGS
improved results screening
800
0
Chair IGS Troposphere WG
• ~50 members
• WG splinter meeting Wed PM: all welcome
• Have almost completed 2012-4 main project:
building cross-technique (GNSS, VLBI,
radiosonde, etc.) tropo-comparison
website/database
• More info @ Dousa et al., “Development Towards
Inter-Technique Tropospheric Parameter
Comparisons…”, PY09, Thu AM
• Special thanks: J Dousa, GOP
number of receivers for which files submitted
ps
• Rapids: orbits, clocks, EOPs for
00-2359 GPST yesterday; released
by 1550 UTC today
Median RMS, USNO GPS Clocks wrt IGS Rapid Combined, 2010-3
ps
3000
r
• Contribute GPS-based rapid, ultrarapid solutions to IGS Combined
Rapid, Ultra-Rapid Products
14
20
0
u
Produce IGS Final Troposphere Estimates
• ZTD, gradient estimates for every IGS station
• 24-h files (one per station), 5-min estimate
spacing
• 10.3M files downloaded in 2013
• 8% increase in # stations processed/day,
2012->2013
• Improved data screening
• More info @ Byram & Hackman, “IGS Final
Troposphere Product Update,” PS05
Hackman, C, S Byram, V Slabinski and J Tracey, United States Naval Observatory Analysis Center
Report 2012, IGS Technical Report 2012, 86-91, 2013.
Hackman, C, S Byram, V Slabinski and J Tracey, United States Naval Observatory Analysis Center
Report 2013, IGS Technical Report 2013, in press, 2014.
Hackman, C, S M Byram, V J Slabinski, J C Tracey and J R Rohde, USNO Analysis Center Progress
2012-14, PS01, 2014 IGS Workshop, Pasadena, CA, 2014.
NS
2011
This poster summarizes these
developments
50
140
USNO IGS Troposphere Coordination
• It also directs IGS troposphere
activities.
Median WRMS, USNO GPS Orbits wrt IGS Rapid Combined, 2010-3
cm
and J.R.
2
Rohde
Dog GPS, West Palm Beach FL
• USNO has improved its product
accuracy – in some parameters,
nearly 50% – and initiated new
projects since the 2012 IGS
Workshop.
•
•
•
•
•
WRMS, USNO GPS Orbits wrt IGS Rapid Combined
Jan 2010 - May 2014
2Black
J.C.
PURPOSE
USNO RAPID, ULTRA-RAPID (GPS) PRODUCTS
2010
V.J.
1
Tracey
-400
-420
-440
-460
-480
-500
-520
-540
56698
OHI2
WHIT
STJO
ALGO
KARR
56702
56706
MBAR
56710
MJD
SUBTRACT FROM ALGO
Site locations (above), receiver
information (below)
receiver
type
TPS NETG3A
TRIMBLE
NETR9
JAVAD
TRE_G3TH
DELTA
JPS E_GCD
JAVAD
TRE_G3T
DELTA
TRIMBLE
NETR8
TPS NETG3A
antenna type
radome type
clock
AOAD/M_T
none
TRM59800.00
none
80
40
NS
1U.S.
S.M.
1
Slabinski ,
STJO-ALGO
0
WHIT-ALGO
H-maser
-40
MBAR-ALGO
internal
-80
56698
ASH701945B_M
SCIS
internal
TPSCR.G3
TPSH
internal
AOAD/M_T
none
H-maser
OHI2-ALGO
TRM59800.00
SCIS
internal
AOAD/M_T
none
rubidium
56702 56706
MJD
56710
KARR-ALGO
PPP CLOCK DIFFERENCE, GLO - GPS
80
RMS, ns: STJO, 38; WHIT, 18; MBAR, 20; OHI2, 42; KARR, 54
40
STJO-ALGO
GPS-GLONASS System Time differences estimated from
pseudorange measurements; relation to PPP time-estimate
errors. Top: GPS-GLONASS system time offsets estimated
from pseudorange measurements. Middle: ALGO values
subtracted from others. Bottom: Difference between
GLONASS and GPS PPP-derived receiver clock estimates.
Note resemblance to middle plot.
NS
C.
1
Byram ,
update station list
1
Hackman ,
0
WHIT-ALGO
MBAR-ALGO
OHI2-ALGO
KARR-ALGO
-40
-80
56698
56702
56706
56710
MJD
Hugentobler, U and C Hackman, International GNSS Service (IGS) – Products and Models for Precise
GNSS Analyses, COST Action ES1206 Meeting, Munich, Germany, 36 pp, 2014.
Slabinski, V, When Did the Mean Solar Day Equal 86,400 SI Seconds?, 45th Meeting, American
Astronomical Society Division of Dynamical Astronomy, Philadelphia, PA, 2014.
For more information: Christine Hackman, US Naval Observatory, 3450 Massachusetts Ave NW, Washington, DC 20392, USA. Tel: (202) 7621428. e: christine.hackman@usno.navy.mil. Products online: http:/www.usno.navy.mil/USNO/earth-orientation/gps-products